In the field of this invention it is known that radio frequency resources are both scarce and expensive. Hence, in designing and operating cellular-based systems, spectrum efficiency must be optimised. This is critical, particularly in the current wireless communication climate, where several operators may compete for customers within the same frequency band using a number of known spectrum allocation techniques. However, in a scenario involving uncoordinated networks (i.e. where there is no central allocation authority between different networks, such as for example wireless local area networks (LANs) such as 802.11b and Bluetooth™, the digital European cordless telephone (DECT) standard, or other ad-hoc shared-spectrum networks, it is not possible to collate resources centrally.
In effect, mobile stations (MSs) or base stations (BSs) on one network have no knowledge of interference that they are causing to MSs/BSs on the other network. Such networks typically operate using dynamic channel methods that select a channel for operation depending on the level of interference measured on that channel. For example, where multiple TDD systems are operating in a band, on adjacent channels, or on adjacent sites on the same channel, interference between networks (or even spectrum required for a guard band) occurs when one network is transmitting, and another unrelated network is receiving. The predominant form of interference is in the form of BS-to-BS, and MS-to-MS, such as where the downlink transmission of BS is interfering with the uplink of another BS.
FIG. 1 illustrates this existing problem where one BS (Base Station 1) operates in one TDD network, and another BS (Base Station 2) operates in a different TDD network. Inasmuch as the two different TDD networks are uncoordinated they may not be synchronized in time, as shown. In particular, there may be a time 100 where a downlink transmission from BS1 may interference 104 with an uplink transmission for BS2. Similarly, there may be a time 102 where an uplink transmission for BS1 may be interfered with 106 by a downlink transmission from BS2.
This interference could be significantly reduced if the networks were synchronised. However, for smaller unconnected networks there is no central mechanism to force synchronisation, and therefore the networks operated in an uncoordinated manner. This is exacerbated for TDD systems that have no frequency planning, as in unregulated spectrum, e.g. WiFi. As such, these uncoordinated systems do not enable fair access to the available communication resources for each network sharing the resource—that is one network may so degrade the quality of the other to effectively prevent it from operating properly.
Thus, there exists a need in the field of the present invention to provide an apparatus and a method of sharing a communication resource that encourages a fair allocation of resources, particularly in an uncoordinated network scenario, wherein the abovementioned disadvantages may be alleviated.
Skilled artisans will appreciate that common but well-understood elements that are useful or necessary in a commercially feasible embodiment are typically not depicted or described in order to facilitate a less obstructed view of these various embodiments of the present invention.